These appear quite good for studying buffers and tone controls.
One of these has a junk op amp onboard (replacement is easy), and the other has a transistor buffer (maybe). I think they're excellent for study and play. There's also a bridged transistor amp with a VCA chip pre (maybe). This larger model appears to have the same VCA chip as one of my preamp kits, so I'm curious if theirs hums or not.
I bought a 13.5w, a 30w, and an 80w to play with, because of their interesting pre-drive stages. For me, its easiest to study when there's a real live example on my desk, and it is more interesting to see it all applied.
Thank you!!

I already have powerful hifi amps aplenty. The real point of my purchase of the little modules is to study their pre-drive (preamp/buffer/predrive) construction, their tone controls, and really just explore.

I bought them for exploration (play). If the two advertised as digital are actually class D, I'll probably see some smoke (I have "personal issues" with class D). However, I'll let you know if any of these are actually useful (If they don't blow up, if the don't have HF that could damage ears, and if they actually work well). Its not important for my use if these work or not.